I need to convert locations from one geographic coordinate system to another.  The main difficulty I am having is converting between geographic datums (models of the earth).  I don't need software that converts from lat/ long to projected x,y but rather converting from lat/ long in one datum to lat/ long in another. 

I managed to find this node which points to a Perl module Coordinate.pm.  But before I start exploring this (quite old) module I was wondering if anyone either knows of a more recent Perl module or can offer advice on datum shifts in Perl.